1. Field of the Invention
The present invention relates to a semiconductor device.
2. Description of Related Art
Japanese Patent Application Publication No. 09-232597 (JP 09-232597 A) discloses a semiconductor device that includes an Insulated Gate Bipolar Transistor (IGBT) and a diode. In the semiconductor device, the IGBT and the diode are formed in a main region of a semiconductor substrate. Further, a withstand voltage structure is formed in an outer peripheral region between the main region and an end surface of the semiconductor substrate.
In the semiconductor device of JP 09-232597 A, an n-type region (hereinafter, referred to as an outer peripheral back surface n-type region) is formed in a range exposed on a back surface of the semiconductor substrate in the outer peripheral region. The outer peripheral back surface n-type region is electrically conductive with a back surface electrode. Therefore, when the diode is turned on, holes flow from a p-type region in the main region (an anode region of the diode or a body region of the IGBT) toward the outer peripheral back surface n-type region. When the diode performs a reverse recovery operation, the holes present in the outer peripheral region flow toward the p-type region in the main region. Therefore, a current is concentrated in the p-type region in the vicinity of the outer peripheral region of the p-type region in the main region.
Further, in a range exposed on the back surface of the semiconductor substrate in the outer peripheral region, the p-type region (hereinafter, referred to as an outer peripheral back surface p-type region) can be formed in place of the n-type region described above. In the case in which the outer peripheral back surface p-type region is formed in this way, when the IGBT is turned on, the holes are supplied from the outer peripheral back surface p-type region toward a drift region in the outer peripheral region. When the IGBT is turned off, the holes present in the outer peripheral region flow to the p-type region in the main region. Therefore, the current is concentrated in the p-type region in the vicinity of the outer peripheral region of the p-type region in the main region.